Cigarette Smoking and Risk of Type 2 Diabetes Mellitus among Middle-aged and Elderly Japanese Men and Women

For examination of sex- and age-specific relations between smoking and risk of type 2 diabetes mellitus, 39,528 nondiabetic men and 88,613 nondiabetic women aged 40-79 years who underwent health checkups in Ibaraki-ken, Japan, in 1993 were followed through 2002. Risk ratios for diabetes according to smoking habits were calculated using a Cox proportional hazards model. Compared with never smokers, the risk ratio for diabetes among current smokers, after adjustment for age, systolic blood pressure, antihypertensive mediation use, alcohol intake, parental history of diabetes, body mass index, fasting status, blood glucose concentration, total and high density lipoprotein cholesterol levels, and log-transformed triglyceride level, was 1.27 (95% confidence interval (CI): 1.16, 1.38) in men and 1.39 (95% CI: 1.20, 1.61) in women. The excess risk was more pronounced among men with a parental history of diabetes than among men without one. The excess risk among current smokers was observed in both age subgroups (40-59 and 60-79 years). Respective multivariate risk ratios for the age subgroups were 1.37 (95% CI: 1.18, 1.60) and 1.20 (95% CI: 1.08, 1.34) in men and 1.45 (95% CI: 1.18, 1.79) and 1.34 (95% CI: 1.09, 1.66) in women. Smoking was independently associated with increased risk of type 2 diabetes among both middle-aged and elderly men and women.